Current conventional practice provides for the use of movable comfort and cleanliness insoles comprising a combination of an upper wear layer designed to allow perspiration to travel through it, an intermediate layer designed to absorb the perspiration, and a final impermeable layer.
In an insole of this kind, perspiration accumulates in the second layer, but cannot be drained away by the lower, impermeable surface. This insole thus takes a long time to dry, since drying can take place only when the moisture flows in the reverse direction through the first layer.
Furthermore, this type of sole construction risks causing a reverse flow of the water from the intermediate layer to the upper layer during walking, by virtue of the pressures thus generated on this layer.
Patent No. FR 2,629,692 proposes an insole comprising a flexible, absorbent elastic perspiration layer combined, on its lower surface, with a stiffening grid.
The stiffening grid delimits cavities which permit a certain degree of ventilation and evaporation of the moisture through the grid, and constitutes a framework for the insole. However, the ventilation thus created is more or less effective and cannot always be implemented, in particular when the shoe is impermeable and fits tightly. Furthermore, this type of insole does not prevent a transfer of moisture to the rest of the shoe, and this moisture, which remains even when the insole is removed, is difficult to wick away.
Nor does this insole solve the problems associated with the rise of moisture toward the foot under the effect of pressure exerted on the insole during walking or other activity, since the absorbent layer where the moisture is stored remains subjected to the pressure generated by the foot.